java - 需要 JButton 事件支持

Question

我最近回答了一个关于如何在另一个类的主方法中打开登录面板的问题。因为我还没有上过任何 Swing 类(class)(只有基本的 Java 编程)，所以我已经偶然发现了另一个问题。

如何检测用户是否按下了 JPanel 中的按钮并使其执行某些操作。

例如:用户按下登录 -> if (textfield1.getText() == "user"){ 打开另一个 JFrame } -> 等等

这是我的主要代码:

import java.awt.*;
import javax.swing.*;

public class Corendon {

    public static void main(String[] args) {
           showLogin();
    }

    private static void showLogin(){
        Login login = new Login();

        JFrame loginFrame = new JFrame();
        loginFrame.add(login);
        loginFrame.pack();
        loginFrame.setLocationRelativeTo(null);
        loginFrame.setVisible(true);
        loginFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }
}

这是登录类:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Daan
 */
public class Login extends javax.swing.JPanel {

    /**
     * Creates new form Login
     */
    public Login() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNINGds: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jPasswordField1 = new javax.swing.JPasswordField();
        jTextField1 = new javax.swing.JTextField();
        jComboBox1 = new javax.swing.JComboBox();
        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();

        jLabel1.setIcon(new javax.swing.ImageIcon("C:\\Users\\Daan\\Dropbox\\HvA\\Programming\\Corendon\\corendon.png")); // NOI18N

        jLabel2.setText("Username");

        jLabel3.setText("Password");

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Dutch", "English" }));

        jButton1.setText("Login");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        jButton2.setText("Cancel");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
        this.setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                        .addGap(31, 31, 31)
                        .addComponent(jLabel1))
                    .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                        .addGap(45, 45, 45)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(jLabel2)
                            .addComponent(jLabel3)
                            .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGap(14, 14, 14)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addGap(29, 29, 29)
                                .addComponent(jButton2)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(jButton1))
                            .addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, 214, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 214, javax.swing.GroupLayout.PREFERRED_SIZE))))
                .addContainerGap(22, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap(16, Short.MAX_VALUE)
                .addComponent(jLabel1)
                .addGap(18, 18, 18)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel2)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel3))
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jButton2)
                    .addComponent(jButton1))
                .addGap(35, 35, 35))
        );
    }// </editor-fold>                        

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

    }                                        

    // Variables declaration - do not modify                     
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JComboBox jComboBox1;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JPasswordField jPasswordField1;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   


}

所以我尝试在 Login.java 内部工作并使用作为事件处理程序的私有(private)方法。我做了这样的事情:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    String user = jTextField1.getText();
    if(user == "user")  {
         jTextField1.setText("LOL");
    }
}  

只是为了测试它是否真的做了我想要的事情，但是当我按下按钮时它没有做任何事情。之后，我尝试在 main.java 中解决它，我实际上在其中创建了包含 JPanel 的框架。在阅读了大量教程之后，它们总是在同一个 java 文件中创建 JPanel 和 JButton 等(在我的例子中是 main.java)。

那么我如何检测登录按钮是否被按下，然后让它处理 JFrame 并继续执行另一个方法，在该方法中我创建另一个包含信息的 JFrame。

我希望我说得足够清楚，如果不是请告诉我。

编辑:当我将测试代码更改为: user.equals("user") 时，它确实有效。但现在我需要它来处理登录框架并访问 main.java 中的另一个方法。我如何从 Login.java 中的私有(private)方法内部实现此目的？

提前致谢，

Answer 1

But now i need it to dispose the Login frame and access another method in my main.java. How can i achieve this from inside a private method in the Login.java?

这里有一个设计问题。您无法调用任何框架的方法，因为您的 ActionListener 的范围仅限于 Login 面板。怎么解决这个问题呢？实现一个 ActionListener，其可见性足以处理框架。

注意:尽量避免使用 NetBeans GUI Builder(或任何 GUI 生成器)。这很容易，但与亲手制作相比，你会错过很多东西。您甚至可以编写更清晰的代码。但有必要了解Layout Managers

代码示例:此示例说明您可以用不到一半的代码行实现相同的效果。

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class Demo {    

    private void initGUI(){        

        final JTextField textField = new JTextField(20);
        final JFrame frame = new JFrame("Login");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);        

        JButton button = new JButton("Accept");        
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if("user".equals(textField.getText())){
                    frame.dispatchEvent(new WindowEvent(frame, WindowEvent.WINDOW_CLOSING));
                    // or simply frame.dispose()
                } else {
                    JOptionPane.showMessageDialog(null, "Wrong user! Keep trying.", "Login failed", JOptionPane.WARNING_MESSAGE);
                }
            }
        });

        JPanel login = new JPanel(new FlowLayout());
        login.add(new JLabel("User"));
        login.add(textField);
        login.add(button);

        frame.getContentPane().add(login);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }    

    public static void main(String[] args) {        
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Demo().initGUI();
            }
        });
    }
}